net/http: make ListenAndServeTLS treat GetCertificate as a set cert too

ListenAndServeTLS doesn't require cert and key file names if the
server's TLSConfig has a cert configured. This code was never updated
when the GetCertificate hook was added to *tls.Config, however.

Fixes #14268

Change-Id: Ib282ebb05697edd37ed8ff105972cbd1176d900b
Reviewed-on: https://go-review.googlesource.com/19381
Reviewed-by: Russ Cox <rsc@golang.org>

Author: bradfitz

src/net/http/serve_test.go

@@ -1039,12 +1039,30 @@ func TestAutomaticHTTP2_Serve(t *testing.T) {
 }
 
 func TestAutomaticHTTP2_ListenAndServe(t *testing.T) {
-	defer afterTest(t)
-	defer SetTestHookServerServe(nil)
 	cert, err := tls.X509KeyPair(internal.LocalhostCert, internal.LocalhostKey)
 	if err != nil {
 		t.Fatal(err)
 	}
+	testAutomaticHTTP2_ListenAndServe(t, &tls.Config{
+		Certificates: []tls.Certificate{cert},
+	})
+}
+
+func TestAutomaticHTTP2_ListenAndServe_GetCertificate(t *testing.T) {
+	cert, err := tls.X509KeyPair(internal.LocalhostCert, internal.LocalhostKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	testAutomaticHTTP2_ListenAndServe(t, &tls.Config{
+		GetCertificate: func(clientHello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+			return &cert, nil
+		},
+	})
+}
+
+func testAutomaticHTTP2_ListenAndServe(t *testing.T, tlsConf *tls.Config) {
+	defer afterTest(t)
+	defer SetTestHookServerServe(nil)
 	var ok bool
 	var s *Server
 	const maxTries = 5
@@ -1060,10 +1078,8 @@ Try:
 			lnc <- ln
 		})
 		s = &Server{
-			Addr: addr,
-			TLSConfig: &tls.Config{
-				Certificates: []tls.Certificate{cert},
-			},
+			Addr:      addr,
+			TLSConfig: tlsConf,
 		}
 		errc := make(chan error, 1)
 		go func() { errc <- s.ListenAndServeTLS("", "") }()

src/net/http/server.go

@@ -2233,10 +2233,11 @@ func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error {
 // Accepted connections are configured to enable TCP keep-alives.
 //
 // Filenames containing a certificate and matching private key for the
-// server must be provided if the Server's TLSConfig.Certificates is
-// not populated. If the certificate is signed by a certificate
-// authority, the certFile should be the concatenation of the server's
-// certificate, any intermediates, and the CA's certificate.
+// server must be provided if neither the Server's TLSConfig.Certificates
+// nor TLSConfig.GetCertificate are populated. If the certificate is
+// signed by a certificate authority, the certFile should be the
+// concatenation of the server's certificate, any intermediates, and
+// the CA's certificate.
 //
 // If srv.Addr is blank, ":https" is used.
 //
@@ -2258,7 +2259,8 @@ func (srv *Server) ListenAndServeTLS(certFile, keyFile string) error {
 		config.NextProtos = append(config.NextProtos, "http/1.1")
 	}
 
-	if len(config.Certificates) == 0 || certFile != "" || keyFile != "" {
+	configHasCert := len(config.Certificates) > 0 || config.GetCertificate != nil
+	if !configHasCert || certFile != "" || keyFile != "" {
 		var err error
 		config.Certificates = make([]tls.Certificate, 1)
 		config.Certificates[0], err = tls.LoadX509KeyPair(certFile, keyFile)